So I washed my house with a pressure washer (vinyl siding) and in some places it left behind some marks where I'm guessing I had the wand too close because it left the place lighter than the surrounding area. Will these marks fade to the match the surrounding or is my house forever tainted?

Depends on what siding you actually have, and how old it is. It could be the lighter areas are actually fully clean, and you just fail at washing the rest. Then again it could be you have stripped off an outer paint layer, and have now ruined your siding.

You could always try more cleaning on some spot that isn't easy to notice or would make a good spot to stand a large planter in front of. But honestly I find a lot of people do a fair bit of damage to their homes with pressure washers, so I hope you knew what you were doing. Well, mostly knew.

Should have gone with a proper clear shingle siding on the place, for a little more money, and a little more work, you get siding that last 120+ years.